The possible influence of environmental factors on the genetic factors studied in the individual projects necessitates that animals are weaned and housed under uniform and well-controlled circumstances. The Laboratory Animal Core will provide the individual investigators with precise information concerning the normal morphology of the mouse strains to be studied. In addition, it will perform routine postmortem examination on all animals and will process and analyze tissues for morphologic evaluation. The Core will coordinate the sharing of the animals so as to maximize the informational output of the experiments performed in the separate projects. An important aspect will be the routine checking of animals housed under the same conditions, but not part of the actual experiment,s to ensure disease prevention and to potentially document mechanisms responsible for altered lifespan. The Core will thus play a vital role in gaining knowledge on possible interactions between genetic and environmental factors which is of the utmost importance for all individual investigators.